1. Field of the Invention
The invention pertains to gear transmissions for louver type signs wherein a plurality of multi-faced elongated louvers having indicia or images appearing thereon are indexed and a plurality of transmissions are driven by a single constantly rotating power source.
2. Description of the Related Art
With a louver type sign, a plurality of long and narrow elements or louvers are mounted in side-by-side relationship and the louvers are indexed to present different faces having indicia defined thereon whereby upon the coplanar alignment of predetermined faces a desired image is produced. The longitudinal edges of adjacent louvers are closely spaced as to permit a continuity of the image appearing on a plurality of adjacent louver faces. Usually, the louvers are provided with three sides or faces and the louvers are usually indexed in a predetermined time cycle as to permit a different louver face to be visible each 30 seconds or so.
It has been the usual practice to simultaneously rotate or index the louvers constituting a complete sign by a belt or chain arrangement operated by an intermittently energized electric motor.
However, it is known to index adjacent louvers with a constantly rotating drive shaft for simultaneous operation or wherein the images defined thereon sequentially become visible and the total image is revealed in a "wave" adding interest to the sign and attracting the viewer's attention for a longer duration, thereby rendering the sign particularly effective.
With constant drive rotation signs and with sequential or wave louver type signs, it is important that the louvers be locked during each indexing to assure alignment of adjacent faces, and to prevent inadvertent partial rotation of the louvers due to external forces, such as wind. In order to lock such indexed louver signs in the desired position, it is known to mount a locking member on the transmission drive shafts which periodically engages a gear mounted upon the transmission output shaft upon which the louvers are mounted, please see U.S. Pat. No. 5,161,421 wherein such a lock mounted upon the transmission drive shaft intermittently meshes with the output shaft gear teeth.
The locking arrangement of the aforementioned patent has the disadvantage of incorporating excessive "play" in the index locking structure because of the necessity of the drive shaft mounted lock to intermesh with the output shaft gears. Such "play" may result in a slight misalignment, and permit a louver to slightly vibrate under high wind conditions, and such vibration is very apparent to the viewer detracting from the desired visual effect.